1. Field of the Invention
The present invention relates to a thin film EL panel comprising forming an EL luminescent layer between a transparent electrode and an opposite electrode and applying voltage to the EL luminescent layer to cause this layer to emit light.
2. Prior Art
The conventional thin film EL panel is of the 6-layer construction having double insulating films and comprising forming a transparent electrode 2, an insulating layer 3, an EL luminescent layer 4, an insulating layer 5 and an opposite electrode 6 on a glass substrate 1 in this order, as shown in FIG. 2. When alternating electric field of several tens Hz to several KHz is applied between the transparent electrode 2 and the opposite electrode 6 in the case of this thin film EL panel, color centers in the EL luminescent layer 4 are excited to emit light. The thin film EL display element of this type has been used as a display for various kinds of devices.
In the case of this thin film EL panel, however, it was sensitive to humidity and when it contacted humidity, its life became extremely short. Therefore, various kinds of measures for preventing water intrusion have been employed.
As shown in FIG. 2, for example, a glass cap 7 seals the thin-film-formed side of the glass substrate 1. Or Oil 8 such as silicon oil is filled in the glass cap 7.
In the case of these thin film EL panels, however, their costs became high and their assembling workability was low because the glass cap 7 was used. When they were sealed only by the glass cap 7, they were influenced by water entering into spaces in the glass cap 7 to deteriorate their luminance and not to make their lives sufficiently long. Even when oil 8 was filled in the glass cap 7, its effect was not sufficient because oil was more likely to pass water therethrough as compared with solid.
Therefore, it has been proposed that a hygroscopic agent is arranged in the glass cap 7, but because the glass cap 7 was U-shaped, it was impossible to fill the hygroscopic agent in the glass cap 7 without any space left and sufficient effect could not be achieved accordingly.